The present invention relates to a horseshoe, especially for trotting horses, notably for the hooves on their forelegs. Horseshoes for this purpose should provide the hooves with the necessary wear protection and should, moreover, have as low a weight as possible, and they should also be extensively pleasant in use for the horses. It is to be noted that the shoes previously developed for the purpose have not been appropriate in all these respects, especially not as far as low weight and accounting for the physiology of the hoof are concerned. The hooves on the forelegs of trotting horses are subject to considerably larger impact than when in the natural condition, and it is well known that top-trained trooting horses are only operative during a very few years, as they develop a decreased mobility of the hoof joints during this period of time.
It has been customary to shoe horse hooves with iron shoes, which extend curved along the rim of the hoof, where the natural wear is at its greatest ,and hereby also the central and rear soft parts are taken into account, as these parts are generally elevated from the ground by positioning the shoe along the rim of the hoof. The concerned soft parts are primarily constituted by a central, longitudinal, backwardly projecting pad named the "frog" which is of increasing width towards the rear, and a pair of cartilage areas on both sides of this, named the "collateral cartilage", which is thus situated at the rear half of the hoof between the rearwardly open rim portion of the hoof and the sides of the "frog".
In connection with specially developed shoes for trotting horses it has been natural still to protect both the hoof rim and the pad or "frog", while the collateral cartilage areas have needed no special protection since they will already be situated above the ground when the hoof rim and the frog are covered with a shoe of appreciable thickness. Therefore, such a special shoe extends arched along the front half of the hoof rim, unto which it is fastened by studs, and therefrom inwards to a central area from which a plate shaped area extends rearwards for covering said pad or "frog". The collateral cartilage areas on both sides of the front end of the frog are hereby left uncovered in an immediately seemingly acceptable manner, whereby the iron shoe need not extend over these areas, which entails a desiredly reduced weight of the shoe.
The said rearwardly projecting plate area which covers the frog cannot be fastened to the hoof, as only the front half of the hoof may be made use of without risk for receiving studs, and therefore a sturdy, transverse middle portion is used to stabilize the backwardly projecting portion. The contour of such a shoe is like a mushroom, through with a central hole in the foremost, almost semi-circular part.
In a known, appropriate method of mounting such shoes a slightly resilient intermediate layer is interposed between the shoe and the hoof, e.g. a leather plate, which is embodied fully covering the entire underside of the hoof. Hereby the collateral cartilage areas are covered, such that they are protected in a gentle manner against tearing from particles on the trotting track, and it is furthermore obtained that the frog area is supported on a softer surface that the hard iron surface of the rearwardly projecting part of the shoe.
A shoe is also known which is adapted to the purpose in shape of a quite thick plate of resilient plastic being shaped nearly in full relative the underside of the hoof, with the plate being embodied with lateral, strongly downwardly projecting ribs for achieving a good set-off against the ground. These shoes are provided with a relatively small central opening, which reduces the weight of the shoe slightly, while they end at the rear along a straight transverse line situated in front of the rear end of the frog of the hoof. In spite of their being used extensively, shoes of such a design may be called a temporary curiosity, inasfar as they do give the hoof an excellent groud grip, but far from make account for the healthiness and the natural conditions of functioning of the hoof. The shoeplate is resiliently bendable to a certain extent, but only about transverse portions, as the ribs stiffen the plate in the lateral direction, and the very poor downwards bendability of the back end of the shoe plate is of limited positive value. However, it is a pronounced disadvantage that the collateral cartilage areas are covered by the plate, this having a quite hard surface, as the collateral cartilage is subject to inappropriate action such that a further chondrification occurs inside the hoof, inhibiting the mobility of the hoof and probably causing soreness of the hoof. Another immediate disadvantage is that the rear edge of the central hole thereof extends across the frog, whereby this bulges down both in front and towards the rear, which inevitably causes soreness in the hoof.
Several further suggestions concerning special shoes are known, but generally the various shoes have well shown one or more of the advantages which an ideal shoe should have, but not at all all of them. In certain cases shoes have been developed intentionally for improving th performance of a healthy horse, but which, when used even for a short time, are disabling for the horse or at least entail such inconveniences and soreness that over time the good results become pronouncedly less good for one and the same horse. A crude example is the abovementioned thick plastic shoes, but even where the shoes are designed based on a better understanding of the functioning and healthiness of the hoof, substantial inconveniences of a more or less recognized kind occur. Use has thus been made of special shock-absorbing shoes or intermediate shoe layers, but even though such a function may be advantageous for the healthiness of the hoof, the shoe is not advantageous in the proper sense of the word if it presents other inconveniences such as a firm pressing against the collateral cartilage area or a neutralizing of the natural function of the frog. Additionally, the shoe is not appropriate even though it is physiologically well-suited for the well-being of the horse but at the expense of the performances of the horse by the physical contact between the shoe and the trotting track, and therefore an ideal shoe should have to take account of both of these aspects, which is the aim of the present invention.
US-A-3,513,915 discloses a shoe which is suitable for general use. The shoe is a plastic plate of resiliently bendable material provided with a hole in the middle for ventilating the frog, but having a thickened outer edge portion corresponding to the shape of a conventional horseshoe. This shoe is not especially suitable for trotting horses, inasfar as it is not provided with special set-off imroving means, and, moreover, it is tapering reawardly due to the conventional shape of the thickening, such that a forward sliding on the track will be braked. In connection with the invention it is reaized that it is essential for the running speed to make an unhindered forward sliding possible while it is in contact with the track by the set-down of the hoof. Furthermore, the far backwardly projecting thickening constitutes an unhealthy permanent covering of the collateral cartilage areas, and the frog will primarily be elevated from ground level, to which it is not naturally destined. As mentioned the frog is a pad which has an essential function as a blood pump, and not least for a trotting horse it will be essential that this pump functions according to its purpose.
By using full plate shoes it may have been obtained to protect the frog, but generally its function as a blood pump has not been taken into account. It is known that it is appropriate to fill out the space between the lower side of the frog and the upper side of the plate if the hoof projects down so far that the frog is elevated from ground level, such that a stimulating contact is established. This may be done by using a casting mass or by interposing a piece of leather for constituting a frog pressure pad. It is correspondingly known to provide for a frog pressure pad as an integrated part of the shoe, cf. US-A-4,513,825, which, besides, only concerns an intermediate layer for use in connection with a metal shoe; a certain shock absorption and pressure distribution is aimed at, but otherwise this particular plate member is not particularly advantageous, because it will exert a firm pressure on the collateral cartilage areas, and not substantially increase the blood pumping effect of the frog.
It is the aim of the present invention to provide a shoe of the full-plate type, which can be used as a technically highly efficient trotting shoe, while also taking the well-being of the horse into account to a previously unknown extent, whereby the combination of these qualities makes the shoe an entirely appropriate shoe.
The invention is based on the consideration that the frog is not just a pad, but actually a strongly required blood pump, the mission of which is to further the blood circulation in the tissue of the hoof for safeguarding a good flexibility in the hoof which is situated in an outer area of the blood circulation system of the animal. The frog should therefore preferably be activated regularly when the hoof is set to the ground, which happens naturally when the horse moves around in its natural condition. It will still be desirable to skid protect the frog as far as trotting horses are concerned, as especially their front hooves are generally subject to greater wearing action than in the horse's natural condition, where extremely fast trot is no natural pace, but specifically during trotting the hoof is subject to very great action, whereby it will be advantageous for several reasons if the frog is able to be extra active as a blood pump.
In accordance with advantageous features of the horseshoe of the present invention, the shoe is constituted by a thin plate element which covers the entire hoof surface and is provided with two mutually separated thickened areas, namely, a first arched area extending along the outer rim portion of the front of the element and being provided with transverse grooves which extend over only a part of the thickened rim area so as to leave an unbroken rib portion extending along the sides of the element, as well as a number of transverse rib portions. A second primarily triangular area extends backwards with an increasing width from a front end area which is situated in front of the transverse middle line of the shoe, such that the triangular area is connected with the rear end of the first area through a connection area including a thin plate material.